1. Field of the Invention
The present invention relates to a mounting structure, and in particular relates to a mounting structure for fixing an electronic element to a heat dissipation unit.
2. Description of the Related Art
FIG. 1 shows a conventional semiconductor element mount structure 1, which comprises a semiconductor element 10. The semiconductor element 10 comprises a body 11, a die 12 and a plurality of leads 13. The die 12 is embedded in the body 11. The leads 13 extend out from the body 11, and are electrically connected to a printed circuit board (not shown). The semiconductor element 10 is fixed on a mounting surface 21 of the heat dissipating unit 20 by a screw 30. The heat dissipating unit 20 comprises a heat sink 23 and an interface material 22. The heat sink (fins) 23 is made of a high heat conductive material, such as copper or aluminum. The interface material 22, such as a heat conductive grease material or a heat conductive sheet material, is sandwiched between the semiconductor element 10 and the heat sink 23.
Conventionally, the semiconductor element 10 is fixed on the heat dissipating unit 20 by the screw 30. The heat dissipation performance of the heat dissipation unit therefore is influenced by the material of the heat dissipating unit 20, the flatness of the mounting surface 21 of the heat dissipating unit 20, the screw torque of the screw 30 or the like. IGBT chip is operated under high temperature and low temperature rapidly, the plastic insulant of the IGBT chip is often deteriorated and embrittled thereby, and the IGBT chip cannot sufficiently contact the heat dissipating unit. The heat dissipation efficiency of the IGBT chips reduced, and the IGBT chips reduced is easily damaged. As well, the IGBT chips reduced is fixed by bolt passing therethrough, assembly error may cause short circuit under high voltage environment. Thus, it is difficult to achieve stable heat dissipation performance.
FIG. 2 shows another conventional semiconductor element mount structure 2. A plurality of semiconductor elements 10 are pressed against a heat dissipating unit 20 by a metal strip 30. The metal strip 30 is fixed on the heat dissipating unit 20 by a bolt 31, and the semiconductor elements 10 are sandwiched between the metal strip 30 and the heat dissipating unit 20. However, since the height of each semiconductor element 10 differs from each other, the metal strip 30 cannot sufficiently press all of the semiconductor elements 10, thereby resulting in inefficient heat dissipating performance.